On Aug 25, 10:55 am, sgiddings <[email protected]> wrote:
> Still working on the implementation as this was just a small aspect.
> Still got a number of other problems to overcome before the code is
> stable.

Chris gave good advice.  It was much easier that way.  I was thinking
of modifying the drawCircle function.

http://www.geocodezip.com/v3_polyline_example_arc.html

If you look closely you can see how the red arc misses the points
because the drawArc function honors the radius rather than the point.

  -- Larry



>
> On Aug 25, 6:52 pm, "[email protected]" <[email protected]>
> wrote:
>
> > On Aug 25, 8:51 am, sgiddings <[email protected]> wrote:
>
> > > Hi Larry and Rossko,
>
> > > Ok, I have the solution, which I will share with you.
> > > I cannot claim any credit as it was Chris Veness (of movable-
> > > type.co.uk fame) who supplied it.
>
> > > Firstly to clarify the question -
> > > The two points are at the same radius from the centre point.
> > > The arc must extend from the first point and finish at the second
> > > point.
> > > The issue of clockwise or counter-clockwise is probably situation
> > > specific - for myself the direction is counter-clockwise.
>
> > > Here is his solution as he stated it -
> > >     * find bearing b1 from centre point to point A
> > >     * find bearing b2 from centre point to point B
> > >     * arc[] = point A // initial point in polyline array
> > >     * for (brng = b1; brng <= b2; brng += incr)
> > >     * {
> > >     *   p = new point dist r, bearing brng from centre point
> > >     *   arc[] = p // add this point to polyline array
> > >     * }
> > >     * draw(arc)
>
> > > I was able to implement this pseudo code to my specific needs.
>
> > Are you going to share your implementation with the group?
>
> >   -- Larry
>
> > > Thanks for your help gentlemen.
> > > Simon
> > > On Aug 25, 2:38 pm, "[email protected]" <[email protected]>
> > > wrote:
>
> > > > On Aug 25, 2:34 am, "[email protected]" <[email protected]>
> > > > wrote:
>
> > > > > On Aug 25, 12:23 am, sgiddings <[email protected]> wrote:
>
> > > > > > Hi Larry,
>
> > > > > > In fact, it was your own page that you put in place to help me with
> > > > > > 'donuts' !
>
> > > > > >http://www.geocodezip.com/v3_polygon_example_donut.html
>
> > > > > But I asked for "the map where you tried to adapt it and failed".
>
> > > > > I'm sure I can do it, given time and motivation (it is just math).
>
> > > > The problem as posed is both underspecified (not enough information)
> > > > and over specified (too much information).  So you have to make some
> > > > decisions when you write your code.  For this case you may know the
> > > > solution, but for a general purpose arc routine, you will need to
> > > > address them.
>
> > > > 1. You have a radius, center point and two points on the circle.  What
> > > > if they aren't consistent?  Does the arc go through both points or
> > > > have the specified radius from the center?
>
> > > > 2. There are 2 solutions: big arc and little arc.  What determines
> > > > which way the arc is drawn, clockwise or counter-clockwise?
>
> > > >     -- Larry
>
> > > > > > Simon
>
> > > > > > On Aug 24, 8:35 pm, "[email protected]" <[email protected]>
> > > > > > wrote:
>
> > > > > > > On Aug 24, 11:27 am, sgiddings <[email protected]> wrote:
>
> > > > > > > > I need to draw an arc between two points on the map, which are 
> > > > > > > > defined
> > > > > > > > by a third "centre" point, keeping the same radius.
>
> > > > > > > > Point A is at (48.596190206866830 : -1.5551704322317228)
> > > > > > > > Point B is at (48.610335003092956 : -1.6123447775299600)
> > > > > > > > Centre point is at (48.565630000000006 : -1.6050300000000002)
> > > > > > > > The radius between the centre point and the outer points is 5 Km
>
> > > > > > > > I tried to adapt the polyline circle example but have clearly 
> > > > > > > > not
> > > > > > > > understood what I should do.
>
> > > > > > > > Can anyone help me with this ?
>
> > > > > > > Probably.  Where is the map where you tried to adapt it and 
> > > > > > > failed?
>
> > > > > > >   -- Larry- Hide quoted text -
>
> > > - Show quoted text -

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